JavaScript .isSealed()

The .isSealed() method is used to check if an object is sealed. An object is sealed when it is non-extensible, and all of its properties are non-configurable.

Syntax

Object.isSealed(object_name)

• object_name: The name of the object to be checked.

Examples

Example 1

The following code will determine if the fruits object is sealed or not by using Object.seal() and Object.isSealed() methods:

let fruits = {
  type: 'watermelon',
  price: '$0.99 per pound',
};
console.log(Object.isSealed(fruits));
Object.seal(fruits);
console.log(Object.isSealed(fruits));

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The above code will return the following output:

false
true

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Example 2

The following code will determine if the fruits object is sealed or not by using Object.preventExtensions() and Object.defineProperties() methods:

let fruits = {
  type: 'watermelon',
  price: '$0.99 per pound',
};
console.log(Object.isSealed(fruits));
Object.preventExtensions(fruits);
Object.defineProperties(fruits, {
  type: {
    configurable: false,
    writable: true,
  },
  price: {
    configurable: false,
    writable: true,
  },
});
console.log(Object.isSealed(fruits));

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The above code will return the following output:

false
true

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Note: If type or price property is configurable, then the fruits object will not be sealed.